Divergence of Drosophila melanogaster repeatomes in response to a sharp microclimate contrast in Evolution Canyon, Israel

Abstract

Repeat sequences, especially mobile elements, make up large portions of most eukaryotic genomes and provide enormous, albeit commonly underappreciated, evolutionary potential. We analyzed repeatomes of Drosophila melanogaster that have been diverging in response to a microclimate contrast in Evolution Canyon (Mount Carmel, Israel), a natural evolutionary laboratory with two abutting slopes at an average distance of only 200 m, which pose a constant ecological challenge to their local biotas. Flies inhabiting the colder and more humid north-facing slope carried about 6% more transposable elements than those from the hot and dry south-facing slope, in parallel to a suite of other genetic and phenotypic differences between the two populations. Nearly 50% of all mobile element insertions were slope unique, with many of them disrupting coding sequences of genes critical for cognition, olfaction, and thermotolerance, consistent with the observed patterns of thermotolerance differences and assortative mating.

Keywords: adaptive evolution; genome sequencing; incipient speciation; microsatellite.

Fig. 1.

An X chromosome region characterized by high sequence divergence, coupled with low Tajima’s D values, as well as high TE differentiation.

Fig. 2.

Genomic distribution of microsatellites in Evolution Canyon D. melanogaster.

Fig. 3.

NFS-SFS interpopulation differentiation (F_st) in SNPs and microsatellites across the major chromosome arms.